Okay, this has been a LONG time coming. I've been developing the universe for this idea for two months, and now I think it's finished, so here we go. This is gonna be one long ass text wall, so read the collapsible at your own risk. I'm going to fully explain EVERYTHING.

I'd like suggestions as to how I can improve the tale and if I'm missing anything essential i.e. a plot-hole or something.

The Foundation has come upon an underground city of kinds. I think of the era/architecture as kind of neo-Egyptian, with the Adobe structures but advanced technology and such. Two races co-exist in a kind of quote unquote "peace": The Strangers, and the Higher Folk. The city is called "Reeve".

The Foundation begins to set up a minor presence in the area, assembling a "containment area" for the civilization while keeping the public calmed about the whole ordeal. The Higher Folk find out about the Foundation's plans and begin attacking the Foundation. The Strangers, long since tired of the Higher Folk's oppression, assist the Foundation in not only resisting the attacks, but ending the attacks by attacking and rioting against the security forces, and later the government.

I plan on making multiple parts to this tale, as it's going to take a while to get through a lot of the plot of this tale.

The Strangers are a race of thin, sleek humanoids. The differences between males and females is nothing more than the obvious lack of/addition of breasts, but that's about it.

- - -Appearance- - -
Skin is white as a sheet. Their faces are mainly featureless, holding anywhere between two to eight eyes arranged in certain patterns, with no visible nose or mouth. Their arms are usually thin, but built with really strong muscular tissue, as is the rest of their body. Their hands are long and thin, with fingers that are more like claws. Their legs are large, ending in one point instead of feet, which means they have to balance themselves. Due to the lack of friction, they can run very fast, and they don't leave footprints when they move. They usually wear one long jumpsuit, often colored black or grey, and above all that, a long, dark cloak, usually with a hood.

- - -Language/Culture- - -
The Strangers use an odd language of tones matched together, so speaking with them sounds like they're simply humming to you. Most of them know some levels of English, however.

In terms of culture, they don't celebrate any form of holiday, often residing in peace in smaller communities around the city. Most of them are happy with outsiders, but will often act with distain when nearby the Higher Folk.

The higher folk are a race of massive humanoids that have dominance over the Strangers and the city. They operate the entire government and treat the Strangers like slaves. Their bodies are made to be really featureless, and there isn't a difference between male and female.

- - -Appearance- - -
Their bodies are featureless, looking like white humanoids, except much more bulky. They bear no resemblance to a Stranger, and are much less intelligent. Their dominance relies entirely on the fact that a Higher Folk can basically knock a Stranger cold with one aimed punch to the face, and they don't have to try.

- - -Language/Culture- - -
The Higher Folk speak English, though they refer to it as "Higher Speech". They cannot replicate the Stranger's language, however.

They dominate the city's culture. There are no holidays, but celebrations are held often to keep morale up in the community. Most Higher Folk have Strangers for servants and base-level workers, but act like the Strangers are slaves.

This feels quite basic right now. So there's two races, one of which has enslaved the other (despite the enslaved race being "superior") who fight in a civil war that the Foundation gets involved in. And that's it. Why should I care about these humanoids? Why should the Foundation? I think a better way to do this might be they fight this long and bloody civil war while the Foundation try very hard to stop any of their war efforts from breaching containment.

The Strangers might as well have giant neon signs above their heads saying "these are the good guys, root for them". And why do they all wear the same clothes? Are those slave clothes? If the Higher Folk are so stupid why haven't the Strangers tried a revolution before, using their superior technology, intelligence, strategic planning, etc? Both the Strangers and Higher Folk seem like generic good guys and bad guys respectively.

I think looking at holidays isn't really enough insight into culture, either. Do they have religion(s)? What traits are valued most among Strangers? Do they follow capitalism? Do they have their own form of currency? Outside of slavery, what problems exist in the Higher Folk government system? If all Higher Folk are giant assholes who treat Strangers like dirt (which they seem to be), why? Is there equality among Higher Folk? Do they all see this as "fair"? Are there Higher Folk who believe they deserve more while other members of their race deserve less?

There's a lot of information missing here, it's hard to invest in either of these cultures when they're both so bland. I think Civil War as a plot has merit as long as I'm genuinely invested in both sides (or even just one side), which I'm not right now. The Foundation accidentally starting a revolution is interesting, but I think the one-sided nature of the conflict makes it a little dull. Maybe they help the Strangers take over, then the Strangers want to explore the Earth and the Foundation are forced to put the Higher Folk (who don't want to leave) back in charge in order to actually keep them contained.